Radio receiver



N0v.7,1944. L E, E MCDONALDQJR 2,361,953

RADIO RECEIVER Filed July 10, 1941 3 Sheets-Sheet l Nov. 7, 1944.

E. F. MCDONALD, JR

RADIO RECEIVER Filed July l0, 1941 5 Sheets-Sheet 2 Nov. 7, 1944. E, F MCDONALD, JR i 2,361,953

RADIO RECEIVERl Filed Jul,r '10, 1941 5 Sheets-Sheet 3 @www Patented Nov. 7, 1944 a UNITED STATES PATENT 4`4OFFICE 2,361,953 v i l l RADIO RECEIVER v `Eugene F. McDonald, Jr., Chicago, Ill." i Application July 10,1941, seria-1N. 401,326` 4 claims. 01.12.50-14) This invention .relates to .radio receivers and more particularly to circuits .and antenna struc-V ture for radio receivers designed for short wave reception ort-for reception in both the broadcast band and short wave bands` The .invention has particular application to radio receivers of the Vportable vtype having selfcontained batteries .but may .be employed with any type Vof receiver. In its most specific aspect theinvention relates to apparatus for enhancing the reception of signals Aby `a `receiver positioned within a shielding structure such as an automobile, airplane, train, ship, etc. provided With Windows or other openings.

Such radio receivers have been provided with loop antennas connected 'to the input circuit ci the set by a flexible connector,A the antenna having vacuum cup or other suitable means for quickly attachably and Adetachably securing the antenna to a supporting surface such as the glass f of a window so that the antenna was positioned to receive signal energy even when the set was positioned within a shielding structure. Loop antennas have proved effective for the broadcast band but have not provedeffective for higher frequency bands such as the higher frequency short Wave bands used for short wave broadcasting. In accordance with the presen-t invention an antenna particularly .adapted .for short Wave reception may be connected Lto the set .by a single flexible connector so as to enable the antenna to be positioned adjacent an opening in a shielding structure. This antenna may likewise be pro vided with means ,for quickly ,attachably or detachably securing `the same to a supporting surface and is of the capacity type, which capacity cooperates with `-a tuning .inductance `carried by the set and the capacity Iof a tuning condenser for tuning the input circuit of the set to the desired signal frequency.

It is therefore an--object of the invention to provide an improved antenna and circuit therefor for enhancing reception of radio signals inshort Wave bands.

Another object of the invention. is to provide an improved antenna structure for enhancing i radio signal reception in short Wave bands by a radio receiver positioned within a shielding structure having an opening therein.

.Afurther object of the invention is to provide a portable radio receiver with a ,plurality of antennas capable `of .being .selectively connected to the inputcircuit of the :set .through flexible connectors so that an antenna suitable for a Vdesired frequency. band may be positioned apart from the set .buticonnected thereto nso as to enhance reception'of the desired fsignal frequency.

Other objects and advantages of the inventionv will appearin the following description of pref,` ferred embodiments of the invention shown in; the attached drawings of which Fig. 1 is a schematic .diagramoi a circuit by which antennas may be selectively `.connected to the input circuit of the set;

Fig. 2 is a View similar to Fig. 1 showing ka mod-ined connection;

Fig. 3 is an elevation of `a preferred type of antenna for short wave reception;`

Fig. 4 is asectional view of theantenna of Fig. 3 taken on the line4-4 of Fig. `3; n Fig. 5 is an .elevaticnof a modied form of antenna: 1 y

Fig. 6 is .asectional View vtaken on the line B-B of Fig. 5K; i i

Fig. '7 is an elevationof a further modified form of antenna; l i

Fig. 8 is a sectional view taken on the line .8-.8 ofFig.7; l Fig. 9 is an elevation of another modified form of antenna; f

10 is a sectional View taken on the line Ill- I0 of Fig. 9;

, Fig.` 11 is a .sectional view taken on the line lI--l I of Fig. 9; y

Fig. 12 .is an elevation `of .a still further .modied form of antenna;

. Fig. 13 .is a sectional View taken `on the line 13e-I3 of Fig. 12;

Fig. 14 is an `end View of a portable radio set with part of the casing broken away to show one way of .supporting a plurality of antennas `in .the set; ,1 i

Fig. 15 is an elevation of aloop antenna particularly :suitable for broadcasting reception;

Fig. `16 is a sectional viewcn the line `I 6-16 of Fig. 16; and y Fig. 17 `isla .schematic diagram of a connection enabling a loop antenna to be employed both for .reception `of' signals .in the broadcast band and for reception of signals in a higher frequency band.

Referring more particularly to theidrawings, the antenna In of Fig. 1 may be .any of the an Atennas of Figs. 3l to 13, inclusive, whereas the antenna .Il may be theloop antenna of Figs. 15

and 16 or a similar loop antenna. Signal energy may be fed selectively from either of the antenas` lthe pentode .type `usually employed `for radio frequency amplification .but which may be any other type employed for the input tube of a radio receiver such as a pentagrid converter or mixer. A single-pole double-throw switch I4 may be operated by the usual band switching devices (n-t sh0Wn) of the radio set and with its central contact I5 in its-upper position the loop antenna II is connected across a tuning condenser I6 to form a parallel tuning circuit which in turn is connected across the control grid I2 and the cathode I1 of the tube I3 through a coupling condenser I 8, the coupling condenser I8 being employed to enable an A. V. C. voltage to be applied' to the grid I2 through a resistor I9. 'Ihe loop antenna II is constructed so that its inductance cooperates with the capacity of the condenser I6 to tune the parallel tuning cir ber 34. A rubber vacuum cup 36 may be riveted or otherwise secured through the various members of the antenna and serve as a connector for connecting a iiexible conductor 38 to the metal member 34. Instead of employing a metal place, a grid of conductors 40 may be positioned between insulating members 4I and 42 as shown in Figs. 7 and 8. The conductors 40 may be connected at their midpoints to a common conductor 43 which forms the lead-in for the antenna. The antenna of `Fig. .7 may be provided with a plurality of Vacuum cups 44 for securing the same to a supporting surface.

The antenna of Figs. 9, 10 and 11 may comprise an vinsulating structure 46 in the form of l a ring with a conductor 41 extending around cuit including the loop antenna II and thecon-v denser I6 to a desired frequency in the broadcast band.

When the contact I5 of the switch I4 is in its lower position the antenna Ill is connected to one terminal of a parallel tuning circuit including an inductance 2I and the condenser I6. The value of the inductance 2| is such that it cooperates with the capacity of the condenser I6 and the antenna I0 to tune the input circuit to a desired frequency in a short wave band. It will be apparent that either the condenser I6 or the inductance 2I may be variable and that a plurality of inductances 2 I or condensers I6 with suitable switching arrangements may be provided to adapt the set for reception upon a plurality of short Wave bands and that a plurality of antennas I0 may also be employed for the same purpose.

In Fig. 2 is shown a modified circuit in Awhich the antenna I6 is inductively coupled to an inductance 23 by means of a coil 24 in series with the antenna III. Otherwise the circuit is the same as the circuit of Fig. 1. The coil 24 lis loosely coupled to the inductance 23 so that the tuning circuit including the inductance 23 and the condenser I6 is more nearly independent of variations in effective capacity of the antenna, such as those due to the body capacity of the user of the set or grounded conductors in the vicinity of the antenna I0.

The antenna I0 may have avariety of constructions. A preferred construction is shown in Fig. 3 in which the antenna includes aconductor 21 positioned within a horseshoe shaped insulating structure 28 Whichmay be of cardboard, ber or plastic material and which may be transparent, if desired. A lead-in 29 in the form of an insulated ilexible conductor may be connected to the conductor 21 at 30 andthe insulating structure 28 may be provided with a vacuum cup 3Iproviding for quickly attaching the antenna to a supporting surface ordetaching the antenna from said surface. This construction minimizes obstruction to vision if the antenna is placed upon the transparent material closing a window in a shielding structure such as the Window or windshield of an automobile or airplane.

A modied structure is shown in Figs. 5 and 6 which may include an insulating plate 33 Ato which is attached a metal plate 34 covered by another insulating member 35. The insulating plate 33 may be of any suitable insulating material and the metal plate 34 may be of thin sheet metal orv foil. One of the insulating members 33 or 35 may be of sumcient strength to impart rigidity to the antenna structure and the other merely a thin insulating covering for the memapproximately three sides of the ring. 'Ihe leadin conductor 48 may be connected to the midpoint 49 of the conductor 41 and the insulating structure 46 may be provided with a plurality of vacuum cups 50 hinged thereto by means of hinges 5I so that the antenna may be attached to a supporting surface and positioned at a desired angle to the surface. The antenna of Figs. 9, 10 and 11 also minimizes obstruction to vision if the antenna is positioned upon a transparent panel. The antenna of Figs. 12 and 13 may comprise sheets of insulating member 53 with conductors 54 extending diagonally thereacross and connected together at the midpoints 55. One of the conductors 54 may extend from the antenna in the form of a lead-in 56 for connection to the radio set and the antenna may be provided with a Vacuum cup 51 for securing the same to a supporting surface.

The structure of a portable radio receiverl set illustrated in Fig. 14 shows how a plurality of antenna may be supported in such a set. For example, theset 59 may be provided with a rear closure 60 hinged to the main casing of the set at 6I'. An antenna IIJ for short Wave reception and an antenna I I for broadcast reception may be held in the closure member 6I] by means of pivoted holding members 62. As shown in Figs. 15 and 16, the antenna II may include insulating members 64and 65 in the form of a ring and a coiled conductor 6B may be positioned 4between the members 64 and 65 to form a loop antenna, the ends of the loop extending from the antenna and being supported in the edges of a flexible fabric member 61 to form a connection to the set.

It is noted that in Fig. 14, the capacity antenna I0 is carried by the portable set 59 and has a relatively large confined area and relatively small linear dimensions, the conned area of the capacity antenna I0 being comparable to the size of the portable Set 59. By confined area of the capacity antenna I Il it is understood that I mean that area conned within the outermost edges of the metal forming the capacity antenna. That is, in the capacity antenna shown in Fig. 9 such conned area is substantially equal to the area conned within or bounded by the insulating structure 46.

In Fig. 17 is shown a circuit for employing a loop antenna such as the antenna II of Figs. 15 and I6 for both reception in a broadcast band and in a higher frequency band. A two-pole double-throw switch 1I) may be employed to connect the loop antenna across the tuning condenser I6 when the central contacts 1I and 12 are in their lower position for operation of the antenna II as a loop antenna. With this connection the inductance of the antenna II in cooperation with the capacity of the condenser I6 forms a parallel tuning circuit for tuning to a desired frequency in the broadcast band.

When the contacts 'II and 'I2-of the switch 10 the condenser I6 so that the antenna II functions as a capacity type antenna. It has been found that this circuit may be employed for medium frequency bands above the broadcast band. The antennas of Figs. 3 to 13 are preferred for short wave reception when the set is positioned within a shielding structure when an antenna such as those shown in Figs. 3 to 13 is positioned adjacent an opening in the shielding structure. It will thus be seen that I have provided an antenna structure and receiving system enabling a portable or othervtype of radio receiver to be employed under adverse conditions for reception, for receiving snort Wave sig` nals as well as both broadcast signals and short wave signals.

While I have disclosed the preferred embodiments of my invention, it is understood that the details thereof may be varied within the scope of the following claims.

I claim:

l. In a portable radio receiving set of such size to be conveniently carried by a person and provided with a self contained capacity antenna and operative under normal conditions to receive radio signals, the improvement which comprises means for enhancing reception of said signals under abnormal conditions when said set is positioned within a shielding structure having an opening therein, said means comprising an elongated flexible member electrically connecting said capacity antenna to said set, and means provided on said capacity antenna constructed and arranged for quickly attachably and detachably securing the same to a surface in any one `of a plurality of positions relative to said opening and apart from said set, said capacity antenna having a large confined area relative to its largest linear dimension and comparable to the surface area of a side of said set,

said capacity antenna being arranged to be placed entirely within the confines of said opening in the shielded structure such that elemental parts of said antenna are near the center of said opening where signal reception is optimum.

2. In a portable radio receiving set of such size to be conveniently carried byA a person and provided with a self contained capacity antenna and operative under normal conditions to receive radio signals, the improvement which comprises means for enhancing reception of said signals under abnormal conditions when said set is positioned within a shielding structure having an opening therein, said means comprising an elongated ilexible member electrically connecting said capacity antenna to said set and vacuum cups carried by said capacity antenna for quickly attachably `and detachably securing the same to surfaces, including vertical surfaces, in any one of a plurality of positions relative to said opening and apart from said set, said capacity antenna having a large conned area relative toits largest linear dimension and comparable to the surface area of a side of said set, said capacity antenna being arranged to be placed entirely within the confines of said opening such that elemental parts of said antenna are near the center of said opening in the shielded structure where signal reception is optimum.

3. In a portable radio receiving set of such size to be conveniently carried by a person and provided with a self contained capacity antenna and operative under normal conditions to receive radio signals, the improvement which comprises means for enhancing reception of said signals under abnormal conditions when said set is positioned within a' shielding structure having an opening therein, said means comprising an elongated flexible member electrically connecting said capacity antenna to said set, and means provided on said antenna constructed and arranged for quickly attachably and detachably securing the same to a surface in any one of a plurality of positions relative to said opening and apart from said set, said antenna including an insulating plate with a capacity plate secured thereto and movable as a unit therewith, said capacity plate having a large confined area relative to its largest linear dimension and comparable to the surface area of a side of said set, said capacity plate being arranged to be placed entirely within the confine-s of said opening such that elemental parts of` such capacity plate are near the center of said opening in the shielded structure where signal reception is optimum.

4. In a portable radio receiving set of such size to be conveniently carried by a person and provided with a self contained capacity antenna and operative under normal conditions to receive radio signals, the improvement which comprises means for enhancing reception of said signals under abnormal conditions when said set is positioned within a shielding structure having an opening therein, said means comprising an elongated flexible member electrically connecting said antenna to said set, and means provided on said capacity antenna constructed and arranged for l quickly attachably and detachably securing the same to a surface in any one of a plurality of positions relative to said opening and apart from said set, said antenna including an insulating plate secured thereto, said insulating plate having a plurality of vacuum cups secured thereto to constitute said means constructed and arranged for quickly attachably and detachably securing the same to said surface, said capacity plate having a large confined area relative to its largest linear dimension andv comparable to the surface area of a side of said set, said capacity plate being arranged to be placed entirely within the confines of said opening such that elemental parts of such capacity plate are near the center 'of said opening in the shielded structure where signal reception is optimum.

EUGENE F. MCDONALD, Jn. 

